This invention relates to a dental adhesive composition for bonding acrylic resin to teeth and, more specifically, to a dental adhesive composition for restorative teeth and for bonding dental composite material (composite resin) to enamel and dentin. A bonding force with respect to dentin is particularly needed for restorative teeth.
With a conventional adhesive for bonding restorative composite resin to an enamel, a bonding strength higher than 100 kg/cm.sup.2 that meets clinical requirements well enough is obtained between an enamel and the restorative composite resin. This is true even when an enamel is treated by acid etching using phosphoric or citric acid, then washed with water and dried, and finally coated with a primer which is composed of a methacrylic ester monomer and a curing agent and shows no adhesion to the dentin. However, as only poor adhesion to a dentin is obtained by using the primer having no adhesion to the dentin, various dentin treatment solutions or primers considered to be adhesive have been proposed. For instance, Japanese Patent Publication No. 55-30768 describes a phosphoric ester compound as being adhesive to the dentin, but it fails to give the aforesaid high bonding strength, as measured by the present inventors.
Japanese Patent Laid-Open No. 54-12338 discloses a functional monomer 4-methacryloxyethyl trimellitic anhydride (hereinafter 4META for short), and the "Journal of the Japan Society for Dental Apparatus and Materials", 23(61), pp. 29-32 (1982) teaches that when a dentin is treated with an aqueous solution of 10% citric acid and 3% ferric chloride and then restored with a restorative filler (4META-containing methyl methacrylate/tri-n-butyl borane/polymethyl methacrylate), a bonding strength of 12-18 Mpa is obtained. When measured by the present inventors, however, such a high bonding strength could not be obtained. Furthermore, when using a chemical polymerization type restorative composite resin made up of a redox initiating system of a tertiary amine-benzoyl peroxide, a problem will arise in connection with the reaction between the tertiary amine and 4META.
In view of the present state of the art where no clinically efficacious adhesive is obtained yet, as mentioned above, we have made an effort to achieve an adhesive which is not only improved in terms of its adhesion to a dentin but serves to reinforce a dentin as well, and so have accomplished the present invention.